Cementum contains the greatest amount of fluoride in all mineralized tissues

Function of cementum attachment site for the periodontal ligament.Protects the underneath tissues.the loss of cementum will expose dentin to the oral environment.Assists in maintaining the length and width of periodontal ligament space by apposition of new cementum. Assists in repairing fractures by restoration of the root by apposition of new cementum.

Tooth development

Root Formation & Cementogenesis the Cervical lobe begins to grow down into the dental sac –elongates and moves away from the dental papilla

it forms a Hertwig's root sheathTypes Of Cementum1-By the location Radicular cementum: The cementum that is found on the root surface

3- by presence of collagen fibrils Fibrillar cementum: Cementum with a matrix that contains well-defined fibrils of type I collagen.

Afibrillar cementum: Cementum that has a matrix devoid of detectable type I collagen fibrils. .

4- By the origin of the matrix fibersThe collagen fibrils of cementum are of three kinds:extrinsic group ( sharpey's fibers ).intrinsic group.Mixed group.

are formed by the cementoblasts It generally corresponds to secondary cellular cementumfound between the sharpey's fibers.

Intrinsic fibre cementumIts is derived as Sharpey’s fibres .They are formed by the fibroblasts of the periodontal ligamentThis type of cementum corresponds with primary cementum

Extrinsic fibre cementumMixed Fiber the collagen fibres of the organic matrix are derived from both extrinsic fibres and intrinsic fibres

Not :There is another classification

Acellular extrinsic fibre cementumCellular intrinsic fibre cementumAcellular Afibrilar cementumIncremental lines of SalterThe appearance of incremental lines in cementum is mainly due to differences in the degree of mineralization, but these must also reflect differences in composition of the underlying matrix

Cemento-dentinal junction The dentin surface upon which cementum is deposited is relatively smooth in permanent teeth.

The cementodentinal junction in deciduous teeth, however, is sometimes scalloped

Cemento-Enamel Junction

Cemento-Enamel Junction

In about 10% of the teeth, enamel and cementum do not meet.

In approximately 30% of all teeth, cementum meets the cervical end of enamel in a relatively sharp line.

In approximately 60% of the teeth, cementum overlaps the cervical end of enamel for a short distance.

Pathology of cementum Root resorption : in the apical portion of the root may occur, however, if orthodontic pressures are excessive and movement is too fast

Pathology of cementum Hypercementosis The excessive build up of cementum on the roots of a toothPathology of cementum Cemental Caries : it increases in older adults as gingival recession occurs from either trauma or periodontal diseasePathology of cementum Cementilcle : are mineralized bodies of cementum found either attached to the cemental root surface or lying free in the periodontal ligament .Pathology of cementum Ankylosis : is the fusion of cementum and alveolar bone with obliteration of the periodental ligament

epithelial diaphragm–encloses the developing primary apical foramen

The function of this sheath is determination of the root shape

Cementum formation in the developing tooth is show by the deposition of dentin along the inner aspect of Hertwig‘s sheath .

the undifferentiated mesenchymal cells derived from the dental sac differentiate into cementoblasts .

These cells have the ultrastructural characteristics typical of cells actively synthesis protein and polysaccharide .

Growth of cementum is a rhythmic process and as a new cementoid is formed, the old one is calcified .

A thin layer of cementoid can be observed on cemental surface which is covered by cementoblasts .

cementoid :the cementum matrix produced by the cementoblasts

The mineralization begins after forming the first layer of matrix.

During matrix formation fibroblasts form collagen fibers (sharpey`s fibers), which become embedded in the matrix to provide attachment of the root to the surrounding bone.

cementoblasts become entrapped in the forming matrix and then known cementocytes .

Cementocytes

Cementocytes are seen located in lacunae in cementum matrix and typically have numerous processes lying in canaliculi .

Light yellow in colorSemi-permeable to variety of material Can be distinguished from enamel by it’s lack of luster and it’s darker hue.Properties of cementum Properties of cementum Properties of cementum cementogenesiscementogenesisMatrix formation

MineralizationCollagen fiber type I

Ground substance

Hydroxy apatite crystals

There are 3 cell types responsible for the cementogenesis:CementoblastsCementocytesFibroblasts

Cementogenesis

Cementum formation in the developing tooth is shown by deposition of dentin along the inner aspect of Hertwig‘s sheath . the undifferentiated mesenchymal cells derived from the dental sac differentiate into cementoblasts

Growth of cementum is a rhythmic process and as a new cementoid is formed, the old one is calcified .

A thin layer of cementoid can be observed on cemental surface which is covered by cementoblasts .

cementoid :the cementum matrix produced by the cementoblasts

The mineralization begins after forming the first layer of matrix.

Coronal cementum: The cementum that forms on the enamel covering the crownAcellular cementum: Cementum without any cells in its matrixThe Types of CementumRoot Formation & Cementogenesis